Abutment.



M. T. THOMPSON.

ABUTMENT.

APPLICATION FILED JUNE 30. 1913.

Pa'tentedSept. 26,1916.

(NI ENTOR T. Thamipson, 5. .1

OBNE! WITNESSES: V %ZZQ/ZKMW MILTOZll' T. THOMPSON, 0F KEOKUK, IOWA.

ABUTMENT.

Specification of Letters Yatent.

Patented Sept. 26, 1916.

Application filed June 30, 1913. Serial NO. 776,525.

To all whom it may concern Be it known that I, illnxron T. TrroMr- SON, a citizen of the United States of America, residing at the city of Keokuk, State of Iowa, have invented a certain new and useful Abutment, of which the following is such a full, clear, and exact description as will enable any one skilled in the art to which it appertains to make and use the same, reference being had to the accomlmnying drawings, forming part of this specification.

My invention relates to a novel form of abutment and retaining wall for bridges or viaducts, being particularly adapted for use where a stream or other obstacle is crossed by means of fills of earth or other material in combination with one ormore bridge spans, and its object is to produce an entirely efiicient and satisfactory structure of this character which can be constructed much more cheaply than any form of abutment now in use.

Heretofore, in constructing abutments, it has been necessary to erect a massive column of stone or other material whose weight would be sufiicient to cause it to permanently resist the stresses to which it is subjected tending both to overturn it and push it from its foundations. My improved form of abutment can, however, be built with a relatively small quantity of material, the various stresses being resisted in the manner hereafter pointed out.

In the accompanying drawings, Figure l is a side elevation; Fig. 2, a plan view of the abutment; and Fig. 3, a front elevation.

The abutment is formed from concrete, located on a suitable foundation, the front portion being semicircular gential continuations or projections 2. In the upper edge of the central portion a bridge-seat 3 is formed. The upper edge of the wall slopes downwardly from each side of the bridge seat in substantial conformity to the natural maximum slope of an earth fill. The upper edges of the tangential continuations are provided with downwardly inclined faces l and these continuations extend into and under the earth or other material of the fill.

5 are reinforcing rods spaced as shown and extending longitudinally from one extremity of the abutment to the other and preferably positioned midway between the and having tanouter and inner faces. It will be noted that the highest rod 5 shown in the drawings has its central portion positioned near the top of the abutment. The lines (5 in Fig. 2 represent the outline the toe of a fill will naturally assume when applied to the abut-- ment, and the lines 7 in Figs. 1 and 3, the slope of the fill along the outer face of the abutment.

The abutment is subjected to a bursting pressure and the semicircular form of the front makes it possible to resist this pressure with a smaller quantity of material than necessary with other forms. This is due to the fact that the stresses set up in the semicircular structure by the pressure of the fill are all in the direction of the longitudinal axes of the reenforcing members and, therefore, neither the wall as a whole, nor any part thereof, is ever called upon to act as a beam or a slab, as is the case where pressure is applied to a plane surface supported at either extremity or at various points. The tangential termini, being buried under the slope of the earth, prevent the pressure generated by the fill inside the semicircle causing it to spread apart or become distorted. The steel or iron reinforcing rods are strained in direct proportion to the pressure of the material retained and equally all the way around the wall.

The pressure of the material within the abutment also tends to overturn it and to slide it off its foundation. These tendencies are resisted by the fact that the shape of the abutment is such that the center of gravity falls-much farther back from its face than if the same amount of concrete were employed in the ordinary way. In addition to this, the burial of the extremities adds greatly to the stabilityboth on account of the direct pressure of material resting over these extremities and on account of the skin friction or adhesion on their inside and outside faces.

Employing the invention herein described, I have built an abutment twentysix feet high but only fifteen inches thick from bottom to top, which has stood several months without showing any sign of strain or disalinement. An abutment of this height built in the ordinary way would require about four times as much material and would even then be less dependable as a permanent structure.

Having fully described my invention, What I claim as neiand desire to secure by LettersPatentofthe United States is:

1. A unitary concrete abutment and retaining wall for earth fills, comprising a substantially semi-circular portion and long rearwardly extending continuations of the 'alls of said portion having inclined upper edges and extending a substantial distance into and under the earth of the fill, the weight of said cont-intuition walls, the skin friction between them and the earth and the weight of the earth above them sutlicing to resist thepressure of the earth of the till tending to overturn the abutment, and means reinforcing the '2 ll in the direction of its length.

A unitary concrete abutment and retaining .wall for earth fills, of substantially uniform thicltness throughout, comprising only a substantially sei'ni-cireular portion, the upper edge of said portion sloping downwardly from each side of the center to conform to the natural slope of the fill, and long rearwardly extending eontinuations of the walls of said semi-circular portion having inclined upper edges and extending a substantial distance into and under the earth of the till, the weight of said continuation walls, the skin friction between them and the earth and the weight of the earth to resist the overturnabove them suttieing earth oi the fill, and

ing pressure of the the earth on the outer sides oi. the rontinuation Walls sutficing to resist the spreading stress of the fill between the walls, and spaced, continuous, reinforcing members extending through the abutment from end to end.

3. A unitary concrete abutment and retaining Wall for earth fills, comprising only a substantially semicircular portion, the upper edge of said portion sloping down- 'ardly from each side of the center, and long rearwardly extending -continuations of the Walls of said portion extendin a sub stantial distance into and under the earth of the till, the weight of said continuation walls, the skin friction between them and the earth and the weight of the earth above them. su'l'iieing to resist the overturning pressure of the earth of the till, and a continuous reinforcing niemberin the abutment extending from one continuation wall through the upper part of the seu'iicircular portion to the other ci'intinuation wall to transmit the overturning movement from the highest portion of the z butnient to the continuation Wall in testimony whereof, I have hereunto set my hand and a'iiixed my seal in the preslmce of the two subscribing witnesses.

I /HLTON T. THOMPSON. [in s] "Witnesses:

Lee G. ifioiimmcy, J. ALBERT Camrr, J r. 

